This invention relates to an information communication terminal including: a voice communication device that transmits and receives voice signals to and from other telephone equipment via public switched telephone networks; a data communication device that transmits and receives data signals of network calls to and from other network terminals via Internet Protocol (hereinafter, referred to as “IP”) networks; and an instant messaging function.
In recent years, IP network calls (so-called IP calls and Internet calls) which are telephone communication means by data communication via the Internet and/or a dedicated line are becoming widely used due to expansion of digital communication networks through the Internet and/or a dedicated line and reduction of charges for Internet use.
However, there are problems in IP network calls as follows. The IP network calls do not cover a communicable range that is covered by conventional public switched telephone networks (hereinafter, referred to as “PSTN”). Also, the IP network calls are disabled in the case of power outage. Therefore, a telephone terminal is proposed which is adapted to communicate both via PSTN and IP networks.
In the telephone terminal configured as above, users can select either network to use by their own selection. Moreover, a technique is proposed to enhance efficient selection of the two networks, in which, when an incoming call is received via a PSTN, a phone number for an IP network call (VoIP phone number) corresponding to the phone number on the other, end is obtained so as to switch the communication network to an IP network (VoIP communication). Such a technique allows prompt switching to IP network calls when it is convenient to use IP networks rather than PSTN.